Hitherto, a rubber polymer containing an oily component is subjected to a crosslinking treatment to provide a so-called oily gelatinous material as described in, e.g., JP-B-54-2661, JP-B-54-4734, and JP-B-2-61496 (the term "JP-B" as used herein means an "examined published Japanese patent application"), and a gelatinous material is obtained by subjecting a rubbery polymer containing water and a water-soluble plasticizer to a crosslinking treatment as described in, e.g., JP-A-2-71731 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
Since such gelatinous materials are usually excellent in shape retention property, flexibility, elasticity, low-temperature insulation property, etc., they are used as a stress dispersing material such as a mat for preventing a mattress injury, arresting sound, a vibration prevention, a head cooling belt, a cooling pillow, etc. Also, recently, by utilizing the sound characteristics of these gelatinous materials, they are utilized for an ultrasonic transmitting medium (sound medium), etc., and development of them for various products have been expected.
In the development of the uses of the gelatinous materials, a means for using an ultrasonic diagnosis apparatus for diagnosing the abnormality of the tissue on the inside of a living body and the pulsation of a bleed stream has been actively practiced as a sound medium. In such an ultrasonic diagnosis, ultrasonic pulses generated from a diagnosis apparatus are applied to the inside of a testee through an ultrasonic probe which is in close contact with the surface of the living body of the testee and waves reflected from the inside of the testee are detected. In this case, if the contact of the probe and the surface of the living body is insufficient and an air layer exists between them at the diagnosis, the applied ultrasonic waves greatly attenuate and a correct diagnosis cannot be made. Therefore, a method of improving the contact by coating the surface of the living body with an oily material such as an animal oil, a vegitable oil, paraffin, polyethylene glycol, etc., a pasty material, or a jelly-like material is usually employed.
However, the above method has problems, such as the surface of the testee becomes sticky and is stained to give an uncomfortable feeling, as well as since an oily material is liable to flow, the oily material cannot be uniformly coated, whereby the diagnosis result is liable to fluctuate. Also, in the case of diagnosing a site near the surface of a testee in an ultraviolet diagnosis, it is necessary to move the focus region of the ultrasonic pulse applied from the probe to the site diagnosed.
Accordingly, since a material which does not have a shape retaining property and is liable to flow, such as an oily material and a jelly-like material, is inferior in its handling properties, the development of a sound medium which has a shape retaining property and can freely change the thickness thereof has been desired.
As materials for solving these problems, gelatinous materials having a shape retaining property, flexibility, and proper elasticity are recently proposed as a sound medium for ultrasonic diagnosis. As such a medium, there are aqueous gels comprising aqueous polymeric materials and water as described in JP-A-59-82838, JP-A-1-146234, etc., and a polyurethane gel having liquid segments as the inside structure as described in JP-A-1-304109, etc.
However, although in the sound medium using the above-described gelatinous material, the disadvantages caused by the conventional oily materials, pasty material, and jelly-like material are overcome, in the case of the aqueous gel, since the gel contains water, there is a problem in custody that water contained in the aqueous gel is evaporated off and also the water content in the medium changes due to the influence of the humidity in the air to lose the flexibility. Also, in the case of the polyurethane gel, the material which can be used therefor is limited and a polyurethane gel useful for practical use has not yet been developed.
On the other hand, in the field of utilizing ultrasonic waves for ultrasonic medical treatment, ultrasonic waves are used for the treatment of chronic painful disease due to the pain-relieving effect, antiphlogistic effect, the effect of mitigating muscular cramp, etc., by applying ultrasonic waves onto the diseased part resulting in a temperature increase of the affected part, acceleration of the circulation at the affected part, acceleration of the permeability of the cell membrane, etc.
If the probe of an ultrasonic medical treatment device is not well contacted with the surface of the living body in the use of aiming such a medical treatment, the ultrasonic energy cannot be sufficiently applied into the body of a testee, whereby the various problems described above when using oily materials or pasty materials occur.